Flame retarded compositions and additive systems therefor

ABSTRACT

1. A FLAME-RETARDANT COMPOSITION COMPRISING A NORMALLY FLAMMABLE POLYMER OF AN OILFIN CONSISTING OF CARBON AND HYDROGEN AND CONTAINING FROM 2 TO 8 CARBON ATOMS HAVING ADMIXED THEREIN A STABILIZING AMOUNT OF A FLAMERETARDING ADDITIVE SYSTEM WHICH CONSISTS ESSENTIALLY OF THE ADMIXTURE OF (A) A HALOGEN-CONTAINING ARYL COMPOUND SELECTED FROM THOSE OF THE FORMULAS   (Y)A-PHENYLENE-(X)N AND (X)M-PHENYLENE-PHENYLENE-(X)M   WHEREIN X IS SELECTED FROM CHLORINE OR BROMINE, Y IS A HYDROCARBON RADICAL OF 1 TO 20 CARBON ATOMS, N IS AN INTEGER OF 3 TO 6, M IS AN INTEGER OF 3 TO 5, AND A IS AN INTEGER OF 0 TO 3; (B) STANNIC OXIDE; AND (C) A HYDROCARBON COMPOUND OF THE FORMULA   R1-(2,3,5,6-TETRA(R1)-1,4-PHENYLENE)-C(-R2)2-C(-R2)2-   (2,3,5,6-TETRA(R1)-1,4-PHENYLENE)-R1   WHEREIN R1 IS HYDROGEN OR A HYDROCARBON RADICAL FREE OF OLEFINIC OR ACETYLENIC UNSATURATION AND R2 IS AN ALKYL RADICAL CONTAINING FROM 1 TO 4 CARBON ATOMS AND WHEREIN SAID COMPOUND (A) IS PRESENT IN AN AMOUNT IN THE RANGE OF 0.5 TO 20 PARTS PER HUNDRED PARTS OF POLYMER, (B) IS PRESENT IN AN AMOUNT IN THE RANGE OF 0.1 TO 10 PARTS PER HUNDRED PARTS OF POLYMER, AND (C) IS PRESENT IN AN AMOUNT IN THE RANGE OF 0.05 TO 10 PARTS PER HUNDRED PARTS OF POLYMER.

United States Patent Ofitice 3,850,882 Patented Nov. 26, 1974 US. Cl. 26045.75 R 6 Claims ABSTRACT OF THE DISCLOSURE Flame-retarded compositions of normally flammable polymers of olefins are provided by admixing with the polymer a flame-retarding additive system consisting essentially of (a) a halogen-containing aryl compound selected from those of the formulas )n m (X)...

wherein R is hydrogen or a hydrocarbon radical free of olefinic or acetylenic unsaturation; R is an alkyl radical containing from 1 to 4 carbon atoms.

This application is a continuation-in-part of copending application Ser. No. 203,830, filed Dec. 1, 1971, now abandoned.

It is known that readily flammable plastics can be made difficultly flammable by the addition of halogen compounds. =FIame-retarded plastic compositions are im portant, especially for the production of electrical insulating coatings which find application such as in house wiring, for small appliances, electronic equipment wire insulation, jacketing, and the like.

However, in rendering a plastic material fire-retardant or difficultly flammable, it is desirable that the physical properties of the plastic material itself not be significantly altered as a result of the addition of the flameproofing agents. Accordingly, it is highly desirable that a retardant system be provided which will effect the desired flame retardancy to the plastic at the lowest possible levels of addition.

It is thus an object of this invention to provide novel flame-retarding additive systems which permit a reduction in the retardant level otherwise required to render the plastic self-extinguishing or nonburning. Another object of the invention is to provide novel flame-retardant plastic compositions in which the physical properties of the host plastic have not been significantly altered. Other aspects, objects and the several advantages of the invention will be apparent to those skilled in the art from the following discussion and the appended claims.

In accordance with this invention, we [have discovered that in rendering normally flammable olefin polymers flame-retardant, the retardant additive level can be substantially reduced by utilizing an additive system or composition which consists essentially of the admixture of (a) a halogen-containing aryl compound selected from those of the formulas (X)rn a )n (X)m wherein X is selected from chlorine or bromine, Y is a hydrocarbon radical of 1 to 20 carbon atoms, n is an integer of 3 to 6, m is an integer of 3 to 5, and a is an integer of 0 to 3; (b) stannic oxide; and (c) a hydrocarbon compound of the formula R R R R R2 R2 QHQ R2 R R R R R wherein R is hydrogen or a hydrocarbon radical free of olefinic or acetylenic unsaturation and R is an alkyl radical containing from 1 to 4 carbon atoms.

The size of the R hydrocarbon radical is not critical; accordingly, there is no absolute limit to the carbon content thereof. However, When R groups are present, they are generally in the range of l to 20 carbon atoms. In addition, when R groups are present, it is sometimes pre ferred that at least one of the groups be in a paraor 4- position on the molecule.

The individual components of the inventive additive system are known compounds and can be prepared according to any conventional means known in the art. Examples of suitable compounds of (a) are:

1,3,5-tribromobenzene 1,3,5 -trichlorobenzene 1,2,3 ,5 -tetrabromobenzene 1,2,3,5tetrachlorobenzene hexabromobiphenyl hexachlorobiphenyl octabromobiphenyl octachlorobiphenyl pentabromotoluene 3,4,5-tribromo-1,2-diethylbenzene pentachloro-tert-butylbenzene 2,4,6-tribromo-1,3,5-trimethylbenzene 2,4,6-tribromol-eicosylb enzene 2,4, 6-trichloro- 1,3-dodecylbenzene.

Examples of suitable compounds of formula '(c) are:

2,3-dimethyl-2, 3-diphenylbutane 2,3-dimethyl-2,3-di (4-isopropylphenyl butane 2,3-dimethyl-2,3-di (4-benzylphenyl) butane 3 ,4-dimethyl-3 ,4-diphenylhex ane 2-methyl-3-isobutyl2,3-di (4-isobutylphenyl butane 5,6-dimethyl-5,6-di 4-cyclohexylphenyl) decane 3 4-diethyl-3,4-di 3 ,4,5-triethylphenyl hexane 2, 3 -dimet'hyl-2, 3 -di( 3 -hex adecylphenyl butane 2,3 -dimethyl-2, 3-di (2,3,4,5,6-pentamethylphenyl) butane 2,3-dimethyl-2,3-di- (4-eicosylphenyl butane and the like and mixtures thereof.

The additive systems of this invention are particular-1y suitable for rendering polypropylene flame-retardant. It is to be understood, however, that the inventive additive systems are broadly applicable to other normally flammable polymers of olefins having from 2 to 8 carbon atoms per molecule. Examples of other suitable polymeric compounds are polymers and copolymers of olefins such as those of ethylene and butene, 2 methyl-propene-l, ethylene-hexene-l, ethylene-propylene copo'lymers, and the like. Blends or mixtures of the above compounds also can be used in this invention.

The polymers of olefins which are stabilized according to the instant invention are commercially available, normally solid resins which can be formed by any of the numerous techniques known in the art. Polypropylene can be formed by the polymerization of propylene in an inert hydrocarbon medium at 25 to 110 C. The effluent from the reactor is treated to remove residual monomer by flashing, for example, solvent and soluble polymer are removed, and the catalyst is deactivated and extracted. Coordination catalysts suitable for polymerizing propylene are exemplified by a titanium halide, prefer-ably TiCl /3AlCl an aluminum compound, preferably a trialkylaluminum or alkylaluminum compound, such as diethylaluminum chloride and, optionally, a Lewis base. However, since the various type-s of polymers of olefins which can be rendered flame-resistant by the additive system of this invention are, as previously indicated, well known and commercially available materials, the process for their production is not considered to form a part of this invention.

The stabilized polymer system of this invention is prepared by admixing com-pounds (a), (b) and (c), as defined above, with the polymer in amounts such that the weight ratio of part (b) per part (a) is in the range of 0.005 to and the weight ratio of part (c) per part (a) is in the range of 0.0025 to 20.

In the use of the adidtive systems of this invention, there is no definite upper limit for the amount of total aditives to be employed. Ordinarily the additives are used at the lowest level which will provide the desired degree of flame retardancy and which will produce the least adverse change in physical properties of the host material. The following ranges generally are employed:

Parts per hundred parts host material (b) stannic oxide 0.1 to 10.-- 0.4 to 4. (c) Hydrocarbon additive 0.05 to 10 0.16 to 1.6.

Preferred The upper limit of total additive incorporated into any normally flammable organic material will vary with each host material. However, for one presently preferred embodiment of this invention, the preferred ranges listed above have been found to be most applicable to polypropylene.

The flame-retarded compositions can be produced in various manners. For example, intimate mixture of the thermoplastic composition and flame-retarding agents of the invention can be achieved by mixing the composition and the bromine compound at an elevated temperature in an extrusion press or a kneader. The two components also can be dissolved in a common solvent, the solution admixed with the polymer and the solvent subsequently removed. The stannic oxide can be added directly to the host plastic material by kneading at elevated temperatures. Other means of incorporating the various additives into the host polymer will be readily apparent to those skilled in the art and, as such, the manner of formulation of the flame-retarded polymeric composition is not considered to be critical to this invention. In addition, in the case of granular or bead-like plastic compositions, the surface of the granule can be coated with the flame-retardants pnlor to further processing.

It is to be understood that the mixture of this invention also can have incorporated therein the usual fillers, dyes, pigments, plasticizers, antistatic agents, stabilizing agents, and the like, if desired. These compounds are well known in the art and, for the sake of brevity, will not be listed here.

The following examples are presented to illustrate the invention, but it is to be understood that the invention is not intended to be limited thereto. In the examples, the parts specified are parts by weight per 100 parts of polymer (p.h.p.).

4 EXAMPLE I Sample preparation A series of samples were prepared for the LOI (limiting oxygen index) testing (described hereafter) by adding the dry ingredient or ingredients of the formulation to a polypropylene fluff and then masticating the mixture in a Brabender Plastognaph under a nitrogen atmosphere for 5 minutes at 200 C., using a rotor speed of 50 r.p.m. The blended sample was then removed hot from the mixing chamber and pressed and cooled under nitrogen to form Aa-inc'h sheet 125 mils). Five specimens of each sample were tested and their values averaged to give the reported LOI value. Specimens were Az-inch x /2 -inch x 4 inches.

Each sample was prepared using 35 grams of polypropylene having a melt flow value of 3 (ASTM D-1238-62, Condition L) which was charged to the mixing chamber along with the additives, such as flame-retardants, stabilizers, adjuvant and the like, of the formulation, The formulations of the samples were as follows:

Parts Grams Polypropylene 35 1 0. 35

1 Varied 0. 6-0. 7

1 2.0 p.h.p. of hexabromobiphenyl or 1.75 p.h.p. of pentabrcmotoluene. (The halide additive was employed in such an amount that a 1.4 percent bromine content of total composition was obtained.)

2 Phenolic antioxidant: Octadecyl[3-(3,5di-t-butyl-4-hydroxyphenyl)]- propiona e.

EXAMPLE II Utilizing a series of samples prepared in accordance with Example I the effectiveness of the additives as a flame-retardant system was determined by measuring the LOI (limiting oxygen index) thereof. The following results were obtained:

Added in amounts sufiicient to give bromine content of 1.4 percent of total composition.

2 2,3-dimethyl-2,3-diphenylbutane.

The above LOI values show that the three-component additive system of this invention provides satisfactory flame-retardant compositions which are superior to conventional antimony trioxide systems.

EXAMPLE III Sample preparation A series of samples were prepared for the LOI testing by adding the dry ingredient or ingredients of the formulation to a polypropylene fluff and then masticating the mixture in a Brabender Plastograph under a nitrogen atmosphere for 5 minutes at 200 C., using a rotor speed of 50 r.p.m. The blended samples were then removed hot from the mixing chamber and pressed and cooled under nitrogen to form As-inch sheet mils). Specimens As-inch x /2-inch x 4 inches were cut from the pressed sheet and tested.

Each sample was prepared using 35 grams of polypropylene having a melt flow value of 3 (ASTM D-1238-62, Condition L) which was charged to the mixing chamber along with the additives such as flame-rctardants, stabilizers, adjuvants and the like of the formulation. The formulation of the samples was as follows:

Parts Grams Polypropylene 100 35 Stannic oxid Varied Halide 1 Varied Bicumyl Varied Antioxidant 3 0.1 0.035

1 Pentabromotoluene.

2 2,3-dimethyl-2,3-diphenylbutane.

3 Octadecyl[3-(3,5-di-t-butyl-4-hydroxyphenyl)] propionate.

EXAMPLE IV Halide Run number additive 1 S1102 S1920: Adjuvant 2 L01 1 Pentabromotoluene. 2 2,3-dimethy1-2,3-diphenylbutane.

The above LOI values show that the three-component additive system of this invention provides satisfactory flame-retardant compositions, which are superior to conventional antimony trioxide systems.

LOI values (minimal volume fraction of oxygen in a slowly rising oxygen and nitrogen atmosphere necessary to sustain burning of a test specimen), where as set forth in the examples, were determined using an apparatus as described in Modern Plastics, November 1966, pages 141, 142, 146, 148 and 192.

The 0 value of air being 0.21 in theory, it is concluded that any resin formulation giving an LOI value greater than 0.21 would be flame-retardant. However, since factors such as product form and construction affect LOI, a value of 0.24 is considered minimal for a flameretardant blend.

Variations and modifications are possible within the foregoing discussion and disclosure, without departing from the spirit or scope thereof.

That which is claimed is:

1. A flame-retardant composition comprising a normally flammable polymer of an olefin consisting of carbon and hydrogen and containing from 2 to 8 carbon atoms having admixed therein a stabilizing amount of a flameretarding additive system which consists essentially of the admixture of (a) a halogen-containing aryl compound selected from those of the formulas a El: m (Em and wherein X is selected from chlorine or bromine, Y is a hydrocarbon radical of 1 to 20 carbon atoms, n is an integer of 3 to 6, m is an integer of 3 to 5, and a is an integer of 0 to 3; (b) stannic oxide; and (c) a hydrocarbon compound of the formula wherein R is hydrogen or a hydrocarbon radical free of olefinic or acetylenic unsaturation and R is an alkyl radical containing from 1 to 4 carbon atoms and wherein said compound (a) is present in an amount in the range of 0.5 to 20 parts per hundred parts of polymer, (b) is present in an amount in the range of 0.1 to 10 parts per hundred parts of polymer, and (c) is present in an amount in the range of 0.05 to 10 parts per hundred parts of polymer.

2. A composition according to claim 1 wherein said compound (a) is present in an amount in the range of 0.8 to 8 per hundred parts of polymer, (b) is present in an amount in the range of 0.4 to 4 parts per hundred parts of polymer, and (c) is present in an amount in the range of 0.16 to 1.6 parts per hundred parts of polymer.

3. A composition according to claim 1 wherein said polymer is a normally solid polypropylene, (a) is pentabromotoluene and (c) is 2,3-dimethyl-2,3-diphenylbutane.

4. A composition according to claim 2 wherein said polymer is a normally solid polypropylene, (a) is pentabromotoluene and (c) is 2,3-dimethyl-2,3-diphenylbutane.

5. A flame-retardant additive composition which comprises (a) a halogen-containing compound selected from those of the formulas wherein X is selected from chlorine or bromine, Y is a hydrocarbon radical of 1 to 20 carbon atoms, n is an integer of 3 to 6, m is an integer of 3 to 5, and a is an integer of 0 to 3; (b) stannic oxide; and (c) a hydrocarbon compound of the formula UNITED STATES PATENTS 3,093,599 6/1963 Tamm et a1 26045.75 3,347,822 10/ 1967 Jenkner 260--45.75 3,420,786 1/ 1969 Weber et .al. 26045.7 3,441,524 4/1969 Burger et al 2602.5

OTHER REFERENCES Combustion and Flame-vol. 1 0, 1966, pp. to 139, article by Fenimore et a1.

V. P. HOKE, Primary Examiner US. Cl. X.R. 

1. A FLAME-RETARDANT COMPOSITION COMPRISING A NORMALLY FLAMMABLE POLYMER OF AN OILFIN CONSISTING OF CARBON AND HYDROGEN AND CONTAINING FROM 2 TO 8 CARBON ATOMS HAVING ADMIXED THEREIN A STABILIZING AMOUNT OF A FLAMERETARDING ADDITIVE SYSTEM WHICH CONSISTS ESSENTIALLY OF THE ADMIXTURE OF (A) A HALOGEN-CONTAINING ARYL COMPOUND SELECTED FROM THOSE OF THE FORMULAS 